Understanding of how the plant cell walls of different plant species respond to pretreatment can help improve saccharification in bioconversion processes. Here, we studied the chemical and structural modifications in lignin and hemicellulose in hydrothermally pretreated poplar and wheat straw using wet chemistry and 2D heteronuclear single quantum coherence nuclear magnetic resonance (NMR) and their effects on cellulose conversion. Increased pretreatment severity reduced the levels of β─O─4 linkages with concomitant relatively increased levels of β─5 and β─β structures in the NMR spectra. β─5 structures appeared at medium and high severities for wheat straw while only β─β structures were observed at all pretreatment severities for poplar. These structural differences accounted for the differences in cellulose conversion for these biomasses at different severities. Changes in the hemicellulose component include a complete removal of arabinosyl and 4-O-methyl glucuronosyl substituents at low and medium pretreatment severities while acetyl groups were found to be relatively resistant toward hydrothermal pretreatment. This illustrates the importance of these groups, rather than xylan content, in the detrimental role of xylan in cellulose saccharification and helps explain the higher poplar recalcitrance compared to wheat straw. The results point toward the need for both enzyme preparation development and pretreatment technologies to target specific plant species.

中文翻译：

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木质素和半纤维素结构的化学性质与水热预处理严重程度相互作用并影响纤维素转化

了解不同植物物种的植物细胞壁如何响应预处理有助于改善生物转化过程中的糖化。在这里，我们使用湿化学和二维异核单量子相干核磁共振 (NMR) 研究了水热预处理的杨树和小麦秸秆中木质素和半纤维素的化学和结构修饰及其对纤维素转化的影响。预处理严重程度的增加降低了 β─O─4 键的水平，同时 NMR 光谱中 β─5 和 β─β 结构的水平相对增加。小麦秸秆在中、高严重度下均出现β─5结构，而杨树在所有预处理严重度下仅观察到β─β结构。这些结构差异解释了这些生物质在不同严重程度下的纤维素转化率差异。半纤维素成分的变化包括在低和中等预处理严重程度下完全去除阿拉伯糖基和 4-O-甲基葡萄糖醛酸基取代基，而发现乙酰基对水热预处理具有相对抗性。这说明了这些基团而非木聚糖含量在木聚糖在纤维素糖化中的有害作用中的重要性，并有助于解释与小麦秸秆相比杨树的抗逆性更高。结果表明需要针对特定​​植物物种的酶制剂开发和预处理技术。半纤维素成分的变化包括在低和中等预处理严重程度下完全去除阿拉伯糖基和 4-O-甲基葡萄糖醛酸基取代基，而发现乙酰基对水热预处理具有相对抗性。这说明了这些基团而非木聚糖含量在木聚糖在纤维素糖化中的有害作用中的重要性，并有助于解释与小麦秸秆相比杨树的抗逆性更高。结果表明需要针对特定​​植物物种的酶制剂开发和预处理技术。半纤维素成分的变化包括在低和中等预处理严重程度下完全去除阿拉伯糖基和 4-O-甲基葡萄糖醛酸基取代基，而发现乙酰基对水热预处理具有相对抗性。这说明了这些基团而非木聚糖含量在木聚糖在纤维素糖化中的有害作用中的重要性，并有助于解释与小麦秸秆相比杨树的抗逆性更高。结果表明需要针对特定​​植物物种的酶制剂开发和预处理技术。木聚糖在纤维素糖化中的有害作用，并有助于解释与小麦秸秆相比杨树的抗逆性更高。结果表明需要针对特定​​植物物种的酶制剂开发和预处理技术。木聚糖在纤维素糖化中的有害作用，并有助于解释与小麦秸秆相比杨树的抗逆性更高。结果表明需要针对特定​​植物物种的酶制剂开发和预处理技术。